Abstract
Environmental variability and site productivity relationships, estimated by means of soil-site equations, are considered a milestone in decision making of forest management. The adequacy of silvicultural systems is related to tree response to environmental conditions. The objectives of this paper are to study climatic and edaphic variability in Mediterranean Maritime pine (Pinus pinaster) forests in Spain, and the practical use of such variability in determining forest productivity by means of site index estimation. Principal component analysis was used to describe environmental conditions and patterns. Site index predictive models were fitted using partial least squares and parsimoniously by ordinary least square. Climatic variables along with parent material defined an ecological regionalization from warm and humid to cold and dry sites. Results showed that temperature and precipitation in autumn and winter, along with longitudinal gradient define extreme site qualities. The best qualities are located in warm and humid sites whereas the poorest ones are found in cold and dry regions. Site index values are poorly explained by soil properties. However, clay content in the first mineral horizon improved the soil-site model considerably. Climate is the main driver of productivity of Mediterranean Maritime pine in a broad scale. Site index differences within a homogenous climatic region are associated to soil properties.
Highlights
Mediterranean environmental conditions, such as water stress, limit forest growth
The great variability in climate, soil and physiographic conditions leads to a great variability of tree species, growth response and productivity, as it is the case of Maritime pine (Pinus pinaster Ait.)
In this species the environmental variability has derived into two groups in the Iberian Peninsula with great differences in growth performance; the Atlantic Maritime pine (AMP), which is more productive and found mainly in areas with an Atlantic climate, and the Mediterranean Maritime pine (MMP), which grows under pure and mesic Mediterranean climate conditions with an irregular precipitation regime and diverse soil origin which, along with stand isolation, has lead to geographic differentiation of tree attributes such as tree height, stem straightness or productivity (Alía et al, 1997; Río et al, 2004; Bravo-Oviedo et al, 2007)
Summary
Mediterranean environmental conditions, such as water stress, limit forest growth. there is a high environmental variability in the Mediterranean region and mesic forest ecosystems such as those found in Central Europe can exist (Scarascia-Mugnozza et al, 2000). Stand forest dynamics is related to site properties and the application of silvicultural systems must be based on the knowledge of current environmental conditions. These properties are often considered to be the foundations of silviculture (Toumey and Korstain, 1947). The first study on applied autoecology in Spain was conducted for Pinus pinaster within an important research program started in the early sixties. These studies first aimed to establish the autoecology of species of genus Pinus, as they were systematically used in restoration programs. Several works have increased the knowledge on tree-environment relation on forestry application for other species (Díaz-Maroto et al, 2007; SánchezPalomares et al, 2007, 2008; Alonso et al, 2010)
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